Unveiling the axonal connectivity between the precuneus and temporal pole: Structural evidence from the cingulum pathways.

Neuroimaging studies have consistently demonstrated concurrent activation of the human precuneus and temporal pole (TP), both during resting-state conditions and various higher-order cognitive functions. However, the precise underlying structural connectivity between these brain regions remains uncertain despite significant advancements in neuroscience research. In this study, we investigated the connectivity of the precuneus and TP by employing parcellation-based fiber micro-dissections in human brains and fiber tractography techniques in a sample of 1065 human subjects and a sample of 41 rhesus macaques. Our results demonstrate the connectivity between the posterior precuneus area POS2 and the areas 35, 36, and TG of the TP via the fifth subcomponent of the cingulum (CB-V) also known as parahippocampal cingulum. This finding contributes to our understanding of the connections within the posteromedial cortices, facilitating a more comprehensive integration of anatomy and function in both normal and pathological brain processes. PRACTITIONER POINTS: Our investigation delves into the intricate architecture and connectivity patterns of subregions within the precuneus and temporal pole, filling a crucial gap in our knowledge. We revealed a direct axonal connection between the posterior precuneus (POS2) and specific areas (35, 35, and TG) of the temporal pole. The direct connections are part of the CB-V pathway and exhibit a significant association with the cingulum, SRF, forceps major, and ILF. Population-based human tractography and rhesus macaque fiber tractography showed consistent results that support micro-dissection outcomes.

A watch, wait, and rescan approach for incidental benign-appearing notochordal lesions of the skull base.

OBJECTIVE: The aim of this study was to describe the natural history of incidental benign-appearing notochordal lesions of the skull base with specific attention to features that can make differentiation from low-grade chordoma more difficult, namely contrast uptake and bone erosion. METHODS: In this retrospective case series, the authors describe the clinical outcomes of 58 patients with incidental benign-appearing notochordal lesions of the clivus, including those with minor radiological features of bone erosion or contrast uptake. RESULTS: All lesions remained stable during a median follow-up of almost 3 years. Thirty-seven (64%) patients underwent contrast-enhanced MRI; lesions in 14 (38%) of these patients exhibited minimal contrast enhancement. Twenty-seven (47%) patients underwent CT; lesions in 6 (22%) of these patients exhibited minimal bone erosion. CONCLUSIONS: These data make the case for monitoring selected cases of benign-appearing notochordal lesions of the clivus in the first instance even when there is minor contrast uptake or minimal bone erosion.

The lateral retrocanthal transorbital endoscopic approach to the middle fossa: cadaveric stepwise approach and review of quantitative cadaveric data.

OBJECTIVE: The lateral retrocanthal transorbital endoscopic approach (LRCTEA) facilitates trajectory to the middle fossa, preserving the lateral canthal tendon and thus avoiding postoperative complications such as eyelid malposition. Here, the authors sought to define the surgical anatomy and technique of LRCTEA using a stepwise approach in cadaveric heads and offer an in-depth examination of existing quantitative data from cadaveric studies. METHODS: The authors performed LRCTEA to the middle cranial fossa under neuronavigation in 7 cadaveric head specimens that underwent high-resolution (1-mm) CT scans preceding the dissections. RESULTS: The LRCTEA provided access to middle fossa regions including the cavernous sinus, Meckel's cave, and medial temporal lobe. The trajectories and endpoints of the approach were confirmed using electromagnetic neuronavigation. A stepwise approach was delineated and recorded. CONCLUSIONS: The authors' cadaveric study delineates the surgical anatomy and technique of the LRCTEA, providing a stepwise approach for its implementation. As these approaches continue to evolve, their development and refinement will play an important role in expanding the surgical options available to neurosurgeons, ultimately improving outcomes for patients with complex skull base pathologies. The LRCTEA presents a promising advancement in skull base surgery, particularly for accessing challenging middle fossa regions. However, surgeons must remain vigilant to potential complications, including transient diplopia, orbital hematoma, or damage to the optic apparatus.

Defining the limits and indications of the Draf III endoscopic approach to the lateral frontal sinus and maximizing visualization and maneuverability: a cadaveric and radiological study.

PURPOSE: The DRAF III procedure has been used for access to the lateralmost part of the frontal sinus. We sought to identify anatomical and radiological measurements as well as modifications that predict the lateral limits of visualization and surgical access after this procedure. METHODS: Seven cadaver heads were imaged with computed tomography scan. The distance from midline to the medial orbital wall (MOWD), midline to the lateral end of the frontal sinus (MLD), the sum of MLDs (SMLD), interorbital distance (IOD) and the shortest anteroposterior distance of the frontal recess (APD) were utilized. The ratios MLD/MOWD, and SMLD/IOD were calculated. The same distances were measured on 41 CT scans. Orbital transposition (OT) and partial resection of the piriform aperture (PAR) were performed; the visualization and reach were assessed. The angle of insertion was measured before and after the modifications. RESULTS: Only the ratio MLD/MOWD was consistently predictive of access to the lateral, superior and posterior wall of the frontal sinus. Following the modifications, a visualization of 100% laterally was achieved with the 30- and 45 degree endoscopes and every lateral recess could be reached with the 70 degree suction. A mean increase of the angle of insertion of 25.3 and 59.6% was recorded after OT and PAR, respectively. CONCLUSIONS: IOD rather than APD defines the limits of the Draf III approach to the lateral frontal sinus and MLD/MOWD ratio can serve as a useful preoperative tool. Along to the already described OT, PAR increases visualization and reach of the lateral frontal sinus.

Students' perspective on the interactive online anatomy labs during the COVID-19 pandemic.

PURPOSE: New training methods sprung up using communication technologies after the suspension imposed on Greek Universities due to restrictive measures against the COVID-19 pandemic. The current questionnaire-based study evaluates the efficacy and utility of the interactive online anatomy labs (ONALs) in assisting the assimilation of anatomy and substituting dissection labs during the pandemic. METHODS: ONALs consisting of video recorded demonstrations of dissected cadavers were developed so that real-time dialogue and interaction between tutor and students was feasible. First- and second-year medical students who were taught neuroanatomy and splanchnology and first-year dental students who were taught head and neck anatomy evaluated the ONALs. RESULTS: One hundred and sixty students participated. The 61 students (38.13%) attended the splanchnology, 58 (36.25%) the neuroanatomy, and 41 (25.63%) the head and neck anatomy course. 86.9% of the participants found the ONALs beneficial for their study. The 75.5% with previous experience of a "face-to-face" dissection replied that the ONALs cannot substitute satisfactorily "face-to-face" dissections. 63.8% replied positively to the ONALs maintenance after the pandemic. CONCLUSIONS: The study's novelty is based on the maintenance of the greater possible interaction between tutors and students during the ONALs, in contrast to the previously described usage of dissection educational videos in anatomy. Our findings reinforce the established statement that "a teaching dissection is an irreplaceable tool in anatomy education". However, the ONALs were well-received by the students and can be kept on as a supplementary teaching modality and can be proven quite useful in Medical Schools that lack cadavers.

A stepwise laboratory manual for the dissection and illustration of limbic and paralimbic structures: lessons learned from the Klingler's technique.

BACKGROUND: Three-dimensional relationships within the limbic and paralimbic areas are often hard to grasp. Relevant anatomical structures exhibit a complicated architecture and connectivity and therefore surgical approaches targeting lesions or functional resections in this area pose a distinct challenge. PURPOSE: To provide an educational, comprehensive, systematic and stepwise manual for the dissection and illustration of major limbic structures since there is a gap in the pertinent literature. Further, we aim to offer a thorough yet simplified roadmap for laboratory and intraoperative dissections. METHODS: Twenty (20) normal adult, formalin-fixed cerebral hemispheres were studied through the fiber dissection technique and under the microscope. Stepwise and in tandem medial to lateral and lateral to medial dissections were performed in all specimens aiming to reveal the morphology and spatial relationships of major limbic and paralimbic areas. RESULTS: Fourteen (14) consecutive, discrete and easily reproducible laboratory anatomical steps are systematically described to reveal the intricate anatomy of the limbic and paralimbic structures and their main connections. CONCLUSION: This study offers for the first time in the pertinent literature a focused, step-by-step laboratory manual for the dissection and illustration of the limbic and paralimbic structures. The overreaching goal is to supplement the novice and experienced anatomist and neurosurgeon with a thorough and systematic reference to facilitate laboratory or intraoperative dissections.

Dissociation between visuospatial neglect assessment tasks and its neuroanatomical substrates: a case report.

Visuospatial neglect possesses significant heterogeneity in clinical features and neuroanatomical substrates. Behavioral dissociations on different neglect tasks have been reported in the past, and the investigation of their respective anatomical correlates at cortical and, to a lesser degree, subcortical levels has been attempted in stroke studies. We report a patient with a neoplasm occupying the right ventral post-central gyrus and anterior supramarginal gyrus. The patient was admitted preoperatively with dissociation on the performance of neglect tasks, showing clinical deficits in the line bisection task and clock drawing, but not on the cancelation task. The patient underwent an awake craniotomy for tumor excision. Intraoperative visuospatial mapping was employed by applying direct electrical stimulation (DES) to the supramarginal gyrus and the ventral branch of the superior longitudinal fasciculus (SLF III) during the line bisection task. According to our findings, DES was ineffective at the cortical level, but it induced strong rightward bias when applied subcortically at the SLF III. By combining our preoperative and intraoperative anatomical and clinical data, we suggest that the posterior part of the SLF III might have a distinct role in the perceptual component of neglect. Our findings are discussed within the context of previous literature supporting the notion that particular behavioral features of spatial neglect are mediated by different white-matter connections.

A systematic review of surgical treatments of idiopathic intracranial hypertension (IIH).

Idiopathic intracranial hypertension denotes raised intracranial pressure in the absence of an identifiable cause and presents with symptoms relating to elevated ICP, namely headaches and visual deterioration. Treatment of IIH aims at reducing intracranial pressure, relieving headache and salvaging patients' vision. Surgical interventions are recommended for medically refractory IIH and include CSF diversion techniques, optic nerve sheath fenestration, bariatric surgery and venous sinus stenting. Prospective studies on the surgical options for IIH are scant and no evidence-based guidelines for the surgical management of medically refractory IIH have been established. A search in Cochrane Library, MEDLINE and EMBASE from 1 January 1985 to 19 April 2019 for controlled or observational studies on the surgical treatment of IIH (defined in accordance with the modified Dandy or the modified Friedman criteria) in adults yielded 109 admissible studies. VSS improved papilledema, visual fields and headaches in 87.1%, 72.7% and 72.1% of the patients respectively, with a 2.3% severe complication rate and 11.3% failure rate. CSF diversion techniques diminished papilledema, visual field deterioration and headaches in 78.9%, 66.8% and 69.8% of the cases and are associated with a 9.4 severe complication rate and a 43.4% failure rate. ONSF ameliorated papilledema, visual field defects and headaches in 90.5, 65.2% and 49.3% of patients. Severe complication rate was 2.2% and failure rate was 9.4%. This is currently the largest systematic review for the available operative modalities for IIH. VSS provided the best results in headache resolution and visual outcomes, with low failure rates and a very favourable complication profile. In light of this, VSS ought to be regarded as the first-line surgical modality for the treatment of medically refractory IIH.

The corticotegmental connectivity as an integral component of the descending extrapyramidal pathway: novel and direct structural evidence stemming from focused fiber dissections.

This study opts to investigate the thus far ill-defined intra-hemispheric topography, morphology, and connectivity of the extrapyramidal fibers that originate from the frontoparietal cortex and project to the tegmental area and to explore structural correlations to the pyramidal pathway. To this end, twenty normal adult, formalin-fixed cerebral hemispheres were studied through the fiber micro-dissection technique. Stepwise and in-tandem medial to lateral and lateral to medial dissections were carried out in all specimens. The cortical termination of the fibers under investigation was carefully defined, and their entry zone at the tegmental area was meticulously recorded. We consistently identified the corticotegmental tract (CTT) as a distinct fiber pathway lying in the white matter of the genu and posterior limb of the internal capsule and travelling medial to the corticospinal tract (CST) and lateral to the thalamic radiations. The CTT exhibits a fan-shaped configuration and can be classified into three discrete segments: a rostral one receiving fibers from BA8 (pre-SMA, frontal eye fields, dorsal prefrontal cortex), a middle one arising from areas BA4 and BA6 (primary motor cortex and premotor cortex), and a caudal one stemming from areas BA1/2/3 (somatosensory cortex). The anatomical location, configuration, trajectory, and axonal connectivity of this tract are attuned to the descending component of the extrapyramidal system, and therefore, it is believed to be implicated in locomotion, postural control, motor inhibition, and motor modification. Our results provide further support on the emerging concept of a dynamic, parallel, and delocalized theory for complex human motor behavior.

Mapping the superficial morphology of the occipital lobe: proposal of a universal nomenclature for clinical and anatomical use.

The superficial anatomy of the occipital lobe has been described as irregular and highly complex. This notion mainly arises from the variability of the regional sulco-gyral architecture. Our aim was to investigate the prevalence, morphology, and correlative anatomy of the sulci and gyri of the occipital region in cadaveric specimens and to summarize the nomenclature used in the literature to describe these structures. To this end, 33 normal, adult, formalin-fixed hemispheres were studied. In addition, a review of the relevant literature was conducted with the aim to compare our findings with data from previous studies. Hence, in the lateral occipital surface, we recorded the lateral occipital sulcus and the intraoccipital sulcus in 100%, the anterior occipital sulcus in 24%, and the inferior occipital sulcus in 15% of cases. In the area of the occipital pole, we found the transverse occipital sulcus in 88% of cases, the lunate sulcus in 64%, the occipitopolar sulcus in 24%, and the retrocalcarine sulcus in 12% of specimens. In the medial occipital surface, the calcarine fissure and parieto-occipital sulcus were always present. Finally, the basal occipital surface was always indented by the posterior occipitotemporal and posterior collateral sulci. A sulcus not previously described in the literature was identified on the supero-lateral aspect of the occipital surface in 85% of cases. We named this sulcus "marginal occipital sulcus" after its specific topography. In this study, we offer a clear description of the occipital surface anatomy and further propose a standardized taxonomy for clinical and anatomical use.